=============================================================================
                                 UNITED STATES
                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549
                                 SCHEDULE 13D
                Under the Securities and Exchange Act of 1934

                              (Amendment No. 1)

                      Allison Transmission Holdings, Inc.
               ------------------------------------------------
                               (Name of Issuer)

                                 Common Stock
                ------------------------------------------------
                        (Title of Class of Securities)

                                 01973R101
                ------------------------------------------------
                               (CUSIP Number)

                           Allison Bennington, Esq.
                              ValueAct Capital
                 One Letterman Drive, Building D, Fourth Floor
                          San Francisco, CA  94129
                               (415) 362-3700
                ------------------------------------------------
                 (Name, address and telephone number of Person
                Authorized to Receive Notices and Communications)

                           Allison Bennington, Esq.
                              ValueAct Capital
                 One Letterman Drive, Building D, Fourth Floor
                          San Francisco, CA  94129
                               (415) 362-3700

                             December 12, 2014
                ------------------------------------------------
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D, and is filing this
schedule because of 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the
following box [ ].

Note:  Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 240.13d-7 for other
parties to whom copies are to be sent.

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities,
and for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

This information required on the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 ("Act") or otherwise subject to the liabilities of that section of
the Act but shall be subject to all other provisions of the Act (however, see
the Notes).
=============================================================================


                                SCHEDULE 13D
--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 2 of 14
-----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Capital Master Fund, L.P.
-----------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS (See Instructions)*

   WC*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   British Virgin Islands
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         19,125,204**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        19,125,204**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    19,125,204**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

   10.77%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    PN
-----------------------------------------------------------------------------
*See Item 3
**See Item 2 and 5


                                SCHEDULE 13D
--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 3 of 14
----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   VA Partners I, LLC
-----------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         19,125,204**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        19,125,204**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    19,125,204**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    10.77%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    00 (LLC)
-----------------------------------------------------------------------------
*See Item 3
**See Item 2 and 5


                                SCHEDULE 13D
--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 4 of 14
----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Capital Management, L.P.
-----------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         19,125,204**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        19,125,204**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    19,125,204**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    10.77%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    PN
-----------------------------------------------------------------------------
*See Item 3
**See Item 2 and 5


                                SCHEDULE 13D
--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 5 of 14
----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Capital Management, LLC
-----------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         19,125,204**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        19,125,204**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    19,125,204**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    10.77%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    00 (LLC)
-----------------------------------------------------------------------------
*See Item 3
**See Item 2 and 5


                                SCHEDULE 13D
--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 6 of 14
-----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Holdings, L.P.
---------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

---------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         19,125,204**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        19,125,204**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    19,125,204**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    10.77%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    PN
-----------------------------------------------------------------------------
*See Item 3
**See Items 2 and 5


                                SCHEDULE 13D
--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 7 of 14
-----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Holdings GP, LLC
---------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                        [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                   7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES          8.  SHARED VOTING POWER
   BENEFICIALLY        19,125,204**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH     9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        19,125,204**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    19,125,204**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    10.77%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    00 (LLC)
-----------------------------------------------------------------------------
*See Item 3
**See Items 2 and 5





--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 8 of 14
-----------------------------------------------------------------------------
THE PURPOSE OF THIS AMENDMENT NO. 1 TO SCHEDULE 13D IS TO AMEND THE OWNERSHIP
REPORTS OF THE REPORTING PERSONS AND TO AMEND ITEM 4(PURPOSE OF TRANSACTION),
ITEM 6 (CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
TO SECURITIES OF THE ISSUER), AND ITEM 7 (MATERIAL TO BE FILED AS EXHIBITS).
THE INFORMATION BELOW SUPPLEMENTS THE INFORMATION PREVIOUSLY PROVIDED.

Item 1.     Security and Issuer

       This Schedule 13D relates to the Common Stock (the "Common Stock") of
Allison Transmission Holdings, Inc., a Delaware corporation (the "Issuer").
The address of the principal executive offices of the Issuer is One Allison
Way, Indianapolis, Indiana 46222.

Item 2.     Identity and Background

       This statement is filed jointly by (a) ValueAct Capital Master Fund,
L.P. ("ValueAct Master Fund"), (b) VA Partners I, LLC ("VA Partners I"), (c)
ValueAct Capital Management, L.P. ("ValueAct Management L.P."), (d) ValueAct
Capital Management, LLC ("ValueAct Management LLC"), (e) ValueAct Holdings,
L.P. ("ValueAct Holdings") and (f) ValueAct Holdings GP, LLC ("ValueAct
Holdings GP")(collectively, the "Reporting Persons").

       ValueAct Master Fund is a limited partnership organized under the laws
of the British Virgin Islands.  It has a principal business address of 1
Letterman Drive, Building D, Fourth Floor, San Francisco, CA 94129.

        VA Partners I is a Delaware limited liability company, the principal
business of which is to serve as the General Partner to ValueAct Master Fund.
It has a principal business address of 1 Letterman Drive, Building D, Fourth
Floor, San Francisco, CA 94129.

        ValueAct Management L.P. is a Delaware limited partnership which
renders management services to ValueAct Master Fund.  ValueAct Management LLC
is a Delaware limited liability company, the principal business of which is
to serve as the General Partner to ValueAct Management L.P.  Each has a
principal business address of 1 Letterman Drive, Building D, Fourth Floor,
San Francisco, CA 94129.

       ValueAct Holdings is a Delaware limited partnership and is the sole
owner of  the limited partnership interests of ValueAct Management L.P. and
the membership interests of ValueAct Management LLC and is the majority owner
of the membership interests of VA Partners I.  ValueAct Holdings GP is a
Delaware limited liability company, the principal business of which is to
serve as the General Partner to ValueAct Holdings.  Each has a principal
business address of 1 Letterman Drive, Building D, Fourth Floor, San
Francisco, CA 94129.

       (d) and (e). None of the entities or persons identified in this Item 2
has during the past five years been convicted of any criminal proceeding
(excluding traffic violations or similar misdemeanors), nor been a party to a
civil proceeding of a judicial or administrative body of competent judgment,
decree or final order enjoining future violations of, or prohibiting or
mandating activities subject to, federal or state securities laws or finding
any violation with respect to such laws.



--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 9 of 14
-----------------------------------------------------------------------------

Item 4.     Purpose of Transaction

       On December 12, 2014, Allison Transmission Holdings, Inc. (the
"Company") entered into a Cooperation Agreement (the "Agreement") with VA
Partners I, LLC, ValueAct Capital Master Fund, L.P., ValueAct Capital
Management, L.P., ValueAct Capital Management, LLC, ValueAct Holdings, L.P.,
ValueAct Holdings GP, LLC and Gregory P. Spivy (collectively, the "ValueAct
Group").  The ValueAct Group represented in the Agreement that they
collectively owned 19,125,204 shares (approximately 10.77% of the outstanding
common stock of the Company).

       Pursuant to the Agreement and subject to the conditions set forth
therein, the Company has agreed to appoint Mr. Spivy as a member of the Board
of Directors of the Company (the "Board") if requested by the ValueAct Group
before the 60th day prior to the Company's 2016 annual meeting of
stockholders (the "2016 Annual Meeting"). If Mr. Spivy is appointed to the
Board, the Company will include Mr. Spivy as a Class I Director with a term
to expire at the 2016 Annual Meeting.  The Company's obligation to appoint
Mr. Spivy if requested by the ValueAct Group will cease if the ValueAct Group
no longer holds at least 7.5% of the Company's common stock or any member of
the ValueAct Group breaches the Agreement.  The Company has also agreed that
the ValueAct Group may receive certain information about the Company in
accordance with a confidentiality agreement entered into by the parties.

       The ValueAct Group has agreed to vote for the Board's slate of
nominees for director at the Company's 2015 annual meeting of stockholders.
In addition, during the term of the Agreement, the ValueAct Group agrees,
subject to certain exceptions, that it shall not:

       - make, participate in or encourage any solicitation of proxies or
         consents;

       - deposit any securities of the Company in any voting trust or similar
         arrangement;

       - own in excess of 12% of the Company's stock;

       - sell or transfer shares of the Company's stock to any third party
         such that the third party would own more than 4.9% of the Company's
         stock after such a sell or transfer;

       - effect, propose, participate in or facilitate any tender or exchange
         offer, merger, consolidation, acquisition, scheme, arrangement,
         business combination, recapitalization, reorganization, sale or
         acquisition of material assets, liquidation, dissolution or other
         extraordinary transaction involving the Company or any of its
         subsidiaries;

       - engage in any "short selling" of the Company's stock;

       - call or seek to call any meeting of stockholders;

       - seek representation on the Board, except as set forth in the
         Agreement;


--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 10 of 14
-----------------------------------------------------------------------------

       - seek the removal of any member of the Board;

       - make a request for any stockholder list or other Company books and
         records;

       - take any action in support of or make any proposal or request that
         constitutes:

            - advising, controlling, changing or influencing the Board or
              management of the Company, including any plans or proposals to
              change the number or term of directors or to fill any vacancies
              on the Board;

            - any material change in the capitalization, stock repurchase
              programs and practices or dividend policy of the Company;

            - any other material change in the Company's management, business
              or corporate structure; or

            - seeking to have the Company waive or make amendments or
              modifications to its Certificate of Incorporation or Bylaws, or
              other actions that may impede or facilitate the acquisition of
              control of the Company by any person;

       - disparage the Company, its affiliates or any of its current or
         former officers or directors; or

       - encourage a third party to do any of the foregoing.

       The Agreement terminates on the date that is the earliest of: (i) the
Company's failure to appoint Mr. Spivy to the Board following a request by
the ValueAct Group, (ii) in the event Mr. Spivy is appointed to the Board and
then resigns or is otherwise removed, the failure of the Company to work in
good faith to appoint a mutually acceptable replacement nominee, or (iii) the
60th day prior to the Company's 2016 Annual Meeting.

     The foregoing description of the Agreement is qualified in its entirety
by reference to the full text of the Agreement, which is attached as Exhibit
99.1 to the Issuer's Current Report on Form 8-K dated December 15, 2014 and
incorporated herein by reference.

Item 5.    Interest in Securities of the Issuer

       (a) and (b).  Set forth below is the beneficial ownership of shares of
Common Stock of the Issuer for each person named in Item 2.  Shares reported
as beneficially owned by ValueAct Master Fund are also reported as
beneficially owned by (i) ValueAct Management L.P. as the manager of each
such investment partnership, (ii) ValueAct Management LLC, as General Partner
of ValueAct Management L.P., (iii) ValueAct Holdings, as the sole owner of
the limited partnership interests of ValueAct Management L.P. and the
membership interests of ValueAct Management LLC and as the majority owner of
the membership interests of VA Partners I and (iv) ValueAct Holdings GP, as
General Partner of ValueAct Holdings.  Shares reported as beneficially owned
by ValueAct Master Fund are also reported as beneficially owned by VA
Partners I, as General Partner of ValueAct Master Fund.  VA Partners I,

--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 11 of 14
-----------------------------------------------------------------------------

ValueAct Management L.P., ValueAct Management LLC, ValueAct Holdings and
ValueAct Holdings GP also, directly or indirectly, may own interests in one
or more than one of the partnerships from time to time.  Unless otherwise
indicated below, by reason of such relationship ValueAct Master Fund is
reported as having shared power to vote or to direct the vote, and shared
power to dispose or direct the disposition of, such shares of Common Stock,
with VA Partners I (only with respect to ValueAct Master Fund), ValueAct
Management L.P., ValueAct Management LLC, ValueAct Holdings and ValueAct
Holdings GP.

         As of the date hereof, ValueAct Master Fund is the beneficial owner
of 19,125,204 shares of Common Stock, representing approximately 10.77% of
the Issuer's outstanding Common Stock (which shares may also be deemed to be
beneficially owned by VA Partners I).

        ValueAct Management L.P., ValueAct Management LLC, ValueAct Holdings
and ValueAct Holdings GP may each be deemed the beneficial owner of an
aggregate of 19,125,204 shares of Common Stock, representing approximately
10.77% of the Issuer's outstanding Common Stock.

       All percentages set forth in this Schedule 13D are based upon the
Issuer's reported 177,527,712 outstanding shares of Common Stock as
reported in the Issuer?s Form 10-Q for the quarterly period ended September
30, 2014.

       (c) The Reporting Persons have not made any transactions in the
Issuer's Common Stock in the sixty days prior to the date of this Report.

       (d) and (e)  Not applicable.


Item 6.     Contracts, Arrangements, Understandings or Relationships with
            Respect to Securities of the Issuer

       The information set forth in Item?4 above is hereby incorporated by
reference into this Item?6. The information in this Item?6 is qualified in
its entirety by reference to the Agreement, which is attached as Exhibit?99.1
to the Issuer's Current Report on Form 8-K dated December 15, 2014, and is
incorporated by reference herein.

       Other than as described elsewhere in this Report and as previously
reported, the Reporting Persons have no understandings, arrangements,
relationships or contracts relating to the Issuer's Common Stock which are
required to be described hereunder.


Item 7.     Material to Be Filed as Exhibits

      (1) Joint Filing Agreement.

      (2) Cooperation Agreement, dated December 12, 2014, by and among the
Issuer and the ValueAct Group, filed as Exhibit 99.1  to the Issuer's Current
Report on Form 8-K dated December 15, 2014 and incorporated herein by
reference.


--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 12 of 14
-----------------------------------------------------------------------------
                                  SIGNATURE
          After reasonable inquiry and to the best of his knowledge and
belief, the undersigned certifies that the information set forth in this
statement is true, complete and correct.

                              POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears
below on this Schedule 13D hereby constitutes and appoints Jeffrey W. Ubben,
Bradley E. Singer, G. Mason Morfit and Allison Bennington, and each of
them, with full power to act without the other, his or its true and lawful
attorney-in-fact and agent, with full power of substitution and
resubstitution, for him or it and in his or its name, place and stead, in any
and all capacities (until revoked in writing) to sign any and all amendments
to this Schedule 13D, and to file the same, with all exhibits thereto and
other documents in connection therewith, with the Securities and Exchange
Commission, granting unto said attorneys-in-fact and agents, and each of
them, full power and authority to do and perform each and every act and thing
requisite and necessary fully to all intents and purposes as he or it might
or could do in person, thereby ratifying and confirming all that said
attorneys-in-fact and agents or any of them, or their or his substitute or
substitutes, may lawfully do or cause to be done by virtue hereof.

                              ValueAct Capital Master Fund L.P., by
                              VA Partners I, LLC, its General Partner

                              By:     /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President

                              VA Partners I, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President


                               ValueAct Capital Management, L.P., by
                               ValueAct Capital Management, LLC its
                               General Partner

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President


                               ValueAct Capital Management, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President




--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 13 of 14
-----------------------------------------------------------------------------


                                ValueAct Holdings, L.P., by
                                ValueAct Holdings GP, LLC, its
                                General Partner

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President


                                 ValueAct Holdings GP, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President






--------------------------                          -------------------------
CUSIP NO. 00724F101                                             Page 14 of 14
-----------------------------------------------------------------------------
                                 Exhibit 1

                           JOINT FILING UNDERTAKING

The undersigned parties hereby agree that the Schedule 13D filed herewith
(and any amendments thereto) relating to the Common Stock of Allison
Transmission Holdings Inc., is being filed jointly on behalf of each of them
with the Securities and Exchange Commission pursuant to Section 13(d) of the
Securities Exchange Act of 1934, as amended.

                              ValueAct Capital Master Fund L.P., by
                              VA Partners I, LLC, its General Partner

                              By:     /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President

                              VA Partners I, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President


                               ValueAct Capital Management, L.P., by
                               ValueAct Capital Management, LLC its
                               General Partner

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President


                               ValueAct Capital Management, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President

                                ValueAct Holdings, L.P., by
                                ValueAct Holdings GP, LLC, its
                                General Partner

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President


                                 ValueAct Holdings GP, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 15, 2014     Bradley E. Singer, Vice President